Methods of preparing substituted imidazothiazolium compounds

ABSTRACT

The preparation of acyl substituted phenylimidazo(2,1b)thiazoles is described. They are prepared by acylation of phenylimidazo(2,1-b)thiazoles with an acyl halide or anhydride. They can also be prepared by cyclization of the appropriate substituted thiazole to produce the desired phenylimidazo( 2,1b)thiazoles. The latter compounds are useful for the control of helminths in warm-blooded animals.

United States Patent [191 Spicer et al.

[ Apr. 15, 1975 METHODS OF PREPARING SUBSTITUTED IMIDAZOTHIAZOLIUM COMPOUNDS Inventors: Larry Dean Spicer, Princeton; John James Hand, Trenton, both of NJ.

Assignee: American Cyanamid Company,

Stamford, Conn.

Filed: Nov. 22, 1972 Appl. No.: 308,919

Related U.S. Application Data Division of Ser. No. 234,323, March 13, 1972, Pat. No. 3,792,166, which is a continuation-in-part of Ser. No. 90,141, Nov. 16, 1970, Pat. No. 3,708,490, which is a continuation-in-part of Ser. No. 3,220, Jan. 15, I970, abandoned.

U.S. Cl 260/306.8 F Int. Cl C07d 99/10 Field of Search 260/306.8 F

[56] References Cited UNITED STATES PATENTS 3,274,209 9/ 1966 Ragymackers et al 260/306.7 3,708,490 1/l973 Spicer et al. 260/306.8 F

Primary Examiner-Richard J. Gallagher Attorney, Agent, or FirmErnest Y. Miller [5 7 ABSTRACT 7 Claims, No Drawings METHODS OF PREPARING SUBSTITUTED IMIDAZOTHIAZOLIUM COMPOUNDS This application is a division of application Ser. No. 234,323, filed Mar. 13, 1972 now U.S. Pat. 3,792,166, which is a continuation-in-part of application Ser. No. 90,141, filed Nov. 16, 1970 now US. Pat. 3,708,490, which is a continuation-in-part of application Ser. No. 3,220, filed Jan. 15, 1970, now abandoned.

DESCRIPTION OF THE INVENTION The present invention relates to methods of preparing compounds of the fomula:

where R is hydrogen, alkyl having 1 to 17 carbon atoms, haloalkyl having 1 to 6 carbon atoms, lower alkoxy having lto 4 carbon atoms, lower carboalkoxy loweralkyl, phenyl, halophenyl and lower alkylphenyl NCOR;

. cr1 c I (Step b) i in which lower alkyl has 1 to 4 carbon atoms; R is hydrogen, nitro, halo, trifluoromethyl, formylamino or lower alkanoyl (C -C amino and X is a pharmaceutically acceptable anion and the optically active isomers thereof.

This invention relates to a novel process for the preparation of the above compounds and to the use of such compounds for the control of helminths in warm- NCOR blooded animals.

Synthesis of 7-carboxyacyl-6-phenyl-6,7-dihydro- 5l-l-imidazo[2,l-b]thiazolium (I) salts having the formula:

l, QLU R= "(o 3 NCO; (Step a) KHZ 1m III wherein R R and X are as hereinbefore defined.

With respect to the above process, it should be noted that compounds of Type (II) (i.e., the starting materials) are disclosed by B. Kickhofen and Frohnke, in Ber., 88, 1109 (1955) and A. H. M. Raeymaekers, F. T. N. Allenijn, J. Vanderberk .et al. J. Med. Chem., 9, 545 1966) and are generally prepared by the following reaction sequence.

s 5 NH o n I coca x r [I Y II N N-CHZ-C .HX

R4 5 COR; w base to Neutralize HX N432? I 0 R4 II In the cited references X is halogen, preferably chlorine or bromine; R, is alkyl, nitro, halogen or the like and R is methyl.

We have now found that R may also be hydrogen, alkyl, haloalkyl, lower alkoxy, halophenyl, phenyl or lower alkylphenyl.

The reduction of the aryl ketone (II) to the alcohol (III) (Step a) has also been reported by Raeynaekers et al. for a variety of compounds. Raeymaekers utilizes NaBl-I, (sodium borohydride) as the reducing agent, however, we have found that lithium borohydride and potassium borohydride may also be used.

Step b of the present process is carried out by methods similar to those disclosed by Raeymaekers et al. and yields key intermediate compounds IV. Step b III Step c NCOR; 3g

iting-c wherein R R and X are as hereinbefore defined. Ring closure of formula (IV) compounds to yield formula (1) compounds in which R and R are as described above may be accomplished by: (1) treatment of formula (IV) compounds with the appropriate anhydride at a temperature of about between 50200C., and preferably 90l20C. (2) isomerization of the free base of (IV) in an inert solvent (e.g., tetrahydrofuran or chloroform). The free base is made by neutralization of the HX salt (e.g., basic ion exchange resin, sodium bicarbonate or carbonate solution, or one mole of a trialkylamine). Isomerization is usually carried out at a temperature between 30C. and 100C. but somewhat higher or lower temperatures may be used;

Among the compounds prepared by the process of s 0on R2 LN on H the present invention are, for example; 7-acetyl-6-(mchlorophenyl)-6,7-dihydro-5H-imidazo[2,1- b]thiazolium chloride; 7-acetyl-6,7-dihydro-6-(mtrifluoromethylphenyl )-5I-I-imidazo[ 2, l -b]thiazolium chloride; 7 -acetyl-6-(m-formamidophenyl)-6,7-

dihydro-5I-I-imidazo-[2, l -b]thiazolium chloride; 6-(macetamidophenyl)-7-acetyl-6,7-dihydro-5H- imidazo[2,l-'b]thiazolium chloride; 7-acetyl-6-(mbromophenyl)-6,7-dihydro-5I-I-imidazo[2,1- b]thiazolium chloride; 7-(4-chlorobutyryl)-6,7- dihydro-6-phenyl-5I-I-imidazo[2,l-b]-thiazolium chlorides; 7-(m-chlorobenzoyl)-6,7-dihydro-6-phenyl-5H- imidazo[2,1-b]thiazolium chloride; 6,7-dihydro-7-(pnitrobenzoyl)-6-phenyl-5H-imidazo[2,l-b]thiazolium chloride; 6,7-dihydro-6-phenyl-7-(p-toluoyl)-5H- imidazo[2,l-b]thiazolium chloride; 7-formyl-6,7- dihydro-6-phenyl-5II-imidazo[2,l-b]thiazolium chloride.

In addition to the above compounds and the processes for the preparation thereof, this application also describes the use of such compounds for the treatment of helmenthiasis in warmblooded animals. For such use the compounds are generally dispersed in a pharmaceutically acceptable carrier or diluent and administered as a formulated composition. The compositions used may be in the form of a liquid drench, a bolus, capsule, pill, resinate formulation or dissolved in a liquid carrier for administration as an injectable. Boluses, tablets, pills, and the like may be prepared by admixing the active imidazo[2,l-b] -thiazolium salt with binders and lubricants and compressing the mixtures into the desired forms. Usually such preparations contain from about 5 to 20 percent by weight of the active ingredient. However, this may be varied to allow for variation in size, weight and species being treated. A typical bolus prepared with a compound of the present invention contains approximately 10% by weight of the active ingredient and 90% by weight of diluents such as for example, starch, dicalcium phosphate, cellulose, lactose and dextrose.

Advantageously, injectable formulations may be prepared by dissolving the active ingredient in distilled water, pharmaceutically acceptable alcohols, glycols or the like. Since the compounds of the invention are water soluble, they may be stored as the dry salt and dissolved in water just prior to injection. Stability problems are generally avoided by this practice and shipping costs are measurably reduced.

Where it is desirable to administer the present compounds in admixture with animal feed, we have found that such compounds are generally more acceptable when prepared as resinates utilizing acidic cationic exchange resins and carboxylated cation exchange resins either in hydrogen or alkali metal form. Resins such as the sulfonated polystyrenes prepared from styrene and having 1 to percent by weight of divinyl benzene which functions as a cross-linking agent are among the preferred resins. These include amberlite resins IR- 120, IR-l 12 and DOWEX 50 and 50W.

In practice it is found that the compounds of the invention are effective for controlling a broadspectrum of helminths including Nematodirus, Hoemonchus, Trichostrongylus, Olsophagostomum, Trichuris and Ascaris, which infest animals such as cattle, swine, sheep, dogs, goats, rabbits, guinea pigs and the like.

Usually, effective control is obtained when the com- I pounds are administered at from about 5 to 35 mg./kg. of animal body weight, but higher or lower dose levels may be used as dictated by the size, weight and species of the animal being treated. For example, dose levels as low as 3 mg./kg. of body weight or. as high as 100 mgJkg. of body weight may be used depending upon the animal or animals under treatment. This may result in a dosage unit of from about 0.5 mg. to 500 mg.

DETAILED DESCRIPTION The following examples describe the preparation of representative compounds of this invention and the results obtained in various tests as anthelmintics.

EXAMPLE 1 Preparation of N-( 3 -Phenacy1-4-thiazol-2-ylidene )acetamide The above compound is prepared according to the procedure described by Kickhofen et al. in 78% yield, melting point l48l 52C. Utilizing the appropriate anhydride and phenyl thiazole provides formula (11) compounds referred to in the specification above in which R and R are as described.

EXAMPLE 2 Preparation of N-[ 3-( B-Hydroxyphenethyl )-4-thiazolin-2-ylidene acetamide (Process A, step a) The above compound is prepared by reacting the compound of Example 1 with sodium borohydride by a slight modification of the procedure of Raeymaekers referred to about in 97% yield, melting point 156158C., [lit. melting point 157-l59.]

EXAMPLE 3 Preparation of N-[3-(B-Chlorophenethyl)-4-thiazolin-2-ylidene]hydrochloride acetamide (Process A, step b (79.5%), melting point 162-l65C., dec. One recrystallization of a 5.0 g. sample gives 2.75 g. of analytically pure product, melting point 164-l66C., dec.

Anal. Calcd. for C H N SOCl C, 49.21; H, 4.45; N, 8.3; S, 10.11; C1, 22.35.

Found C, 49.25; H, 4.51;N, 8.63; S, 10.38;Cl, 22.12.

EXAMPLE 4 1 Preparation of 7 -Acetyl-6 ,7 -dihydro-6-phenyl-5l-I-imidazo 2 l -b thiazolium chloride chlorde (Process A, step c) A mixture of 10.0 g. (31.6 mmoles) of the compound of Example 3 and ml. of acetic anhydride is warmed slowly to reflux. Solution is attained ca. C. After refluxing for 2 hours, the solvent is evaporated under reduced pressure. Residual solvent is removed by codistillation with toluene. The residue is warmed with acetone, cooled and the product collected by filtration. This gives 6.92 g. of white crystals, melting point 196201C. A second crop of 0.5 g. is obtained, melting point l96-200C. The mull infrared spectrum of Pat. No. 4,714,503 the product obtained by this procedure is different from the product obtained by present Method However, the NMR is consistent with the expected product and differs only in the water protons when compared with the NMR spectrum obtained in present method.

EXAMPLE Preparation of 7-Acetyl-6,7-dihydro-6-phenyl-5-l-l-imidazo[2,1- b]thiazolium perchlorate (Process A, step c) To a slurry of 1.58 (5 mmoles) of the compound of Example 3, in 50 ml. of chloroform there is added 0.51 g. (5.04 mmoles) of triethylamine in 10 ml. of chloroform. The reaction mixture immediately becomes homogeneous. After refluxing for 2 hours, the reaction mixture is cooled and the solvent evaporated to a gum. Acetone is added and the solid removed by filtration. The white solid, 1.22 g., appears to be mixture of ring closed product and triethyl amine hydrochloride. It is dissolved in water, treated with aqueous sodium filtration, and the precipitate collected by filtrating washed with water and dried. This gives 0.63 g. (2.08 mmoles) 41.5%, melting point l77-l79C., of product. The infrared spectrum is identical to that of the authentic perchlorate salt.

EXAMPLE 6 Preparation of 7-Acetyl-6,7-dihydro-6-phenyl-5H-imidazo[2,1- b]thiazolium chloride (Process A, step c) To a stirred slurry of 1.58 g. (5.0 mmoles) of the chloro hydrochloride of Example 3 in 50 ml. of chloroform, there is added without drying 5.0 g. of Amberlyst A-21. RCH N(CH 4.7-5.0 meq/g. of dry weight. Porosity 2030% Surface Area 20-30 meter/g. Moisture, 45%). After stirring for minutes all of the compound is in solution. The resin is filtered off and washed with chloroform. The filtrate is refluxed for two hours, cooled and the solvent evaporated to a gum. This is warmed with acetone and the oily mixture slowly crystallizes. The solid is filtered off, washed and dried to give 0.77 g. (51.6%), melting point 95l00C. of the chloride salt.

When the ion exchange resin is washed and dried to remove water and the reaction carried out at reflux in the presence of the resin, the yield of product is 41%.

EXAMPLE 7 Following the procedures as described in Examples 8 and 9, but substituting the starting materials with the following compounds:

A. N-[ 3-( ,B-chlorophenethyl )-4-thiazolin-2- ylidene]formamide, hydrochloride. B. N-[3-(B-chlorophenethyl)-4-thiazolin-2- ylidene]4-chlorobutyramide, hydrochloride C. N-[3-(B-chlorophenethyl)-4-thiazolin-2- ylidene]m-chlorobenzamide, hydrochloride. D. p-nitrobenzamide, N[3-(B-chlorophenethyl)-4- thiazolin-Z-ylidene], hydrochloride E. p-tolylamide, N-[B-chlorophenethyl)-4-thiazolin- 2-ylidene], hydrochloride the following products are obtained:

A. 7-formyl-6,7-dihydro-6-phenyl-5H-imidazo[2, l

b]thiazolium chloride B. 7-(chlorobutyryl)-6,7-dihydro-6-phenyl-5H- imidazo 2, 1 -b]thiazolium chloride C. 7-(m-chlorobenzoyl)-6,7-dihydro-6-phenyl-5H- imidazo[2,1-b thiazolium chloride D. 7-(p-nitrobenzoyl)-6,7-dihydro-6-phenyl-5H- imidazo[2,l-b]thiazolium chloride E. 7-(p-toluoyl)-6,7-dihydro-6-phenyl-5H- imidazo[2,l-b]thiazolium chloride EXAMPLE 8 Preparation of 7-Acetyl-6,7-dihydro-6-phenyl-5H-imidazo[2,1- b]thiazolium chloride (Process A, Step c) 12.5 Grams (40.0 mmol.) of N-[3-(l3- chlorophenethyl )4-thiazolin-2-ylidene ]hydrochloride acetamide is partitioned between 50 ml. of water and 100 ml..methylene chloride and then saturated aqueous sodium bicarbonate is added until the aqueous phase showed a pH of near 7.0. The methylene chloride is dried over magnesium sulfate and the removal of the solvent yields an oil (free base of starting material). The oil is heated at reflux temperature for 30 minutes in 10 m1. of methyl isopropyl ketone (boiling point C.). On cooling, 5 solid formed in a reaction and ml. of the acetone along with 10 drops of water is added to the reaction. The product is then filtered and dried to yield 8.0 g. (70% yield). The 7-acetyl derivative is isolated as the monohydrate. The NMR and IR are consistent with the product shown above.

Other 7-acyl compounds are prepared by essentially the same procedure. The 7-acyl compounds are formed when the unring closed compound in its free base form is heated in an inert solvent. The larger acyl groups require higher temperatures so that it is advantageous to employ a solvent like toluene or xylene when the acyl group is isobutryl and to carry out the reaction at the reflux temperature of the solvent.

EXAMPLE 9 Tests Showing Activity of Present Compounds Against Infection with Nematospiroides dubius recorded. Twenty untreated mice are used as controls I and these have 20 to 25 adult worms. Data obtained are reported in Table 1 below as percent reduction of adult worms.

TABLE I Subcutaneous Activity vs. N dubius Reduction Dose of B; E 33 No. of Mice M K. Adult Worms CH H 01 23 6o 89 a I 0 67 29 3O 56 own H 01 LL 6o 99 8 3o he on -c- H 01 8 60 9h 8 3 .75 Li 5 3 c n, a c1 1; 6O 95 c a H 01 23 e 11 h- L 53 i 0 29 ca (on H c1 1; 6o (Sofia-so) 9L; 3 2 4 l; 30 (swim-so) 7o cn ococn cn 3 c1 i 6o 91; a i 3 39 on c1 L 0 100 3 0 1 1 u 3 h- All compounds tested w in sterile water.

DMSO Dimethylsulfoxide.

EXAMPLE 10 Test of present compounds in sheep Animals 7 Western lambs are inoculated with Clostridum Type D 'bacterin and treated with an anthelmintic (8-10 ithout adjustment for salt.

All dissolved water and adjusting the volume to give either 5, 10 or 20% solutions.

Solutions are injected in the shoulder area. All animals are sacrificed 3 or 4 days after treatement. Both 5 abdnasum and small intestines are removed, examined and processed by routine technique for counting worms.

Untreated controls are sacrificed at the same time and efficacy is determined by the following formula:

% Efficacy Avg. No. of Worms in controls No. remaining at Necropsy/Avg. No. in controls Data obtained are give in Table II below:

0 :r t- O\ MSpHOHvGOO WDSOGOEUQI N m lz #5 8 m z 8 cm o3 m o w w Q o e A 8 mm mm o3 m dd 3 m: on mm m mq w lz om mm 03 a 4 o m w 8 w. A 2. E. mm m o w w 8 mos, nd a m mmwnmmo oz mpsom wm\ mz omen ecsomeoo HH mum? of Kentucky); and 95000 Trichostrongylus colubriformis. All three species have been maintained in our laboratory for several years. Animals are inoculated by intrarumenal injection. They are fed a commercial pelleted sheep ration plus hay and kept on concrete.

Material Compounds given by intrarumenal injection are dissolved in 30 ccs water and injected with a 30 cc dispos- .10 able syringe using a 17 or 18 ga. 2 inch needle.

Compounds given subcutaneously are prepared by dissolving a weighed amount of material in distilled In calves, the injection site studies with 7-acetyl5,6- dihydro-6-phenyl-5l-l-imidazo[2,1-b]thiazolium chloride is administered subcutaneously to two calves using a commercial injectable l-TMS (ltetramisole) formulation as the control. A total of 10 sites are used on each calf, five on one side received either 8 or 16 mg./kg. (18.2 or 36.4% solutions) dissolved in waterof the test compound, and five sites on the opposite side receive 8 mg./kg. of l-TMS (7.5% solution). Slight tissue reactions are visible when examined at necropsy 26 to 30 days after injecting at one of five and two of five sites in the calves with the test compound and two of five and three of five with the l-tetramisole injectable.

The reactions which occurred are of such mild nature they might easily have been overlooked. Two of the three reactions with the test compound and two of the five l-tetramisole reactions occurred in the rump. The tightness of the hide at this location made subcutaneous injection more difficult compared to the other sites and the needle may have scratched or penetrated the muscle since some blanching is visible on slicing into the muscle. Of the three reactions with the test compound, two occurr with the concentrated solution (36.4%) at 16 mg./kg. and one with the lesser concentration (18.2% at 8 mg./kg.

We claim:

1. A method for the preparation of compounds of the formula:

where R is hydrogen, alkyl (C to C lower alkoxy (C to C lower carboalkoxy lower alkyl, phenyl, halophenyl, or loweralkylphenyl; R is hydrogen, nitro, halogen, trifiuoromethyl, formylamino or alkanoyl (C amino and X is a pharmaceutically acceptable anion; comprising treating a compound of the formula:

. R2 s fncon L 41: 5:11 on where R and R are as described above, with at least one mole equivalent of a compound selected from the group consisting of thionyl chloride, phosphorus trichloride and phosphorus tribromide to form a compound of the formula:

3 neon n wherein R R are as described above and Y is chlorine or bromine; and treating the thus formed compound with (l) acetic anhydride in an inert organic solvent at a temperature between 50C. and 200C. to produce the ring closed compound; or (2) by neutralization of the thus formed acid salt with a basic ion exchange resin, aqueous sodium bicarbonate or a lower trialkylamine (C C and heating of the thus formed free base in the presence of an inert solvent at a temperature of from about 30C. to C. to form the ring closed product.

2. A method according to claim 1, wherein R is alkyl (C -C and R is lower alkyl phenyl.

3. A method according to claim 1, wherein R is lower alkoxy (C -C and R is trifluoromethyl.

4. A method according to claim 1, wherein R is halophenyl and R is alkanoyl (C -C amino.

5. A method according to claim 1, wherein R, is methyl and R is hydrogen.

6. In a method according to claim 1, the step of heating 2,N-[3-(B-hydroxyphenethyl)-4-triazoline-2- ylidene]acetamide with acetic anhydride at refluxing temperature and recovering 7-acetyl-6,7-dihydro-6- phenyl-5l-l-imidazo[ 2, l -b]thiazolium chloride.

7. A method according to claim 1, wherein a compound of the formula:

S NCOR U 2 n-cn c m is neutralized with a basic ion exchange resin, aqueous sodium bicarbonate or a lower trialkylamine (C and heating of the thus formed free base in the presence of an inert solvent at a temperature of from about 30C. to 100C. to form the ring closed product. 

1. A METHOD FOR THE PREPARATION OF COMPOUNDS OF THE FORMULA:
 2. A method according to claim 1, wherein R1 is alkyl (C1-C17) and R2 is lower alkyl phenyl.
 3. A method according to claim 1, wherein R1 is lower alkoxy (C1 -C4) and R2 is trifluoromethyl.
 4. A method according to claim 1, wherein R1 is halophenyl and R2 is alkanoyl (C1-C4) amino.
 5. A method according to claim 1, wherein R1 is methyl and R2 is hydrogen.
 6. In a method according to claim 1, the step of heating 2,N-(3-( Beta -hydroxyphenethyl)-4-triazoline-2-ylidene)acetamide with acetic anhydride at refluxing temperature and recovering 7-acetyl-6,7-dihydro-6-phenyl-5H-imidazo(2,1-b)thiazolium chloride.
 7. A method according to claim 1, wherein a compound of the formula: 